HIGH-STRENGTH STEEL AND METHOD FOR PRODUCING SAME Russian patent published in 2018 - IPC C21D8/02 C22C38/58 C21D1/19 C21D9/46 C23C2/06 

FIELD: metallurgy.

SUBSTANCE: invention relates to a cold-rolled and annealed steel sheet. To achieve the result, a piece comprising, wt%: 0.10≤C≤0.13, 2.4≤Mn≤2.8, 0.30≤Si≤0.55, 0.30≤Cr≤0.56, 0.020≤Ti≤0,0500, 0020≤B≤0.0040, 0.005≤Al≤0.050, Mo≤0.010, Nb≤0.040, 0.002≤N≤0.008, S≤0.005, P≤0.020, remainder consisting of iron and unavoidable impurities, is heated, is hot-rolled to produce a hot-rolled sheet, cooled and cold rolled, annealed, cooled to a predetermined temperature, kept and cooled to room temperature, wherein the resulting cold-rolled annealed steel sheet has a microstructure consisting, in an area ratio, of martensite and/or lower bainite, said martensite comprises fresh martensite and/or self-tempered martensite, the sum of the area ratios of martensite and lower bainite being between 60 and 95 %, of between 4 and 35 % bainite with a small amount of carbides, of between 0 and 5 % ferrite, and of less than 5 % residual austenite in the form of islands.

EFFECT: increasing the tensile strength and yield strength and providing suitable plasticity.

19 cl, 2 dwg, 5 tbl